Crank bearing for bicycles



Patented Sept. 30, 1941 CRANK BEARING FOR BICYCLES Frank W. Schw inn,1 Chicago, Ill.

Application August 2, 1939, Serial No. 287,897

1 Claim.

My invention relates to crank bearings or the like for bicycles, and especially to a self-aligning increasing the parts inventories, except the adcup and cone bearing therefor such as the pedal crank bearing.

In the ball bearings usually used for journaling pedal cranks, the bearings are of the cup and cone type. The cones are usually mounted on the shaft portion of the crank by threading them thereonto and looking them with lock nu'ts. This is to allow adjustment.` I have found that, due to the fact that the cone or inner race member is mounted on the crank by screw threads, there is often a definite malalignment of the cone, whereby its plane is not accurately at a normal to the axis of the crank, as should be the case. Thus, When the crank rotates, the cone does not run true, but runs something like a swash plate, giving a slight axial oscillation to certain regions on the i-cone; This gives an uneven ball bearing support for the journal and causes localized wear.

The general object of my invention is to elirninate the ill effects of such malalignment of the cone. I propose to do this without addingto the complication of the bearing or adding materially to its expense, and still leave the other functions and `qualities of the bearing unimpaired. J' More specifically,.one object of my invention is to provide an adjustable ball bearing mounting .for apedal crank within the crank hanger or head of a bicycle, which bearing will take both end thrusts and radial thrusts, and prevent rockingof the crank within the bearingbut which will allow considerable practical tolerance in the divergenceof the crank-carried race members from planes normal to the axis of the crank.

c I am aware that ball bearings for radial thrusts have been made with the ball race lof anaouter race ring spherically convexed to permit some universal rocking of the shaft without impairing the fit of the balls, but such bearings are not suitable forpedal crank bearings because they do not take end thrusts, or they do not prevent rocking of the crank axis, or they are not susceptible of being made adjustable to take up wear. j j

` By my invention I have accomplished my obdition of the new cup.

Another object of my invention is a ball `retainer peculiarly adaptednfor this cup and cone type of bearing, since the contour of the ball races makes some kind of retainer necessary for convenient assembly and the conventional designs of ball retainers will not function in this type of bearing.

The foregoing together with further objects,

" features and advantages of my invention are set forth in the following description of specific embodments thereof and illustrated in the accompanying drawing, wherein:

Fig. 1 is a diametrical section through the bearing of a pedal crank in a bicycle;

Fig. 2 is an enlarged detail of Fig. 1;

Fig. 3 is a fragmentary elevation of the balls and ball retainer as seen from the line 3-3 of Fig. 2;

Fig. 3A is a cross-section of the retainer taken on the line 3A-3A of Pig. 3; and

Fig. 4 is a view similar to Fig. 1 but showing a modified arrangement.

In Fig. 1 I have shown a pedal crank ilOHjournaled in the crank head or hanger l I of a bicycle frame. i

The shaft portion |2 of the crank carrles a sprocket fiange |3 at one end adjoining the right crank arm M. The sprocket l5 is mounted on the shaft portion |2 and liesagainst the shoulder ofv the flange |3. The right cone'or inner race ring 16 has a threaded borev by means of which it is screwed on to the right threaded section of the shaft portion l2. This both mounts the cone |6 in place and also looks the sprocket on the shaft portion.

. Adjoining the left crank arm |8, the shaft portion 12 carries a threaded section |9. The left cone or inner race ring 20 is threaded on to this vsection 19 and locked in the desired adjusted jective by a simple change in.the cups only,

without substantially increasing the cost of, or adding complications to, the bearing and without change in the other parts now customarily used in pedal crank bearings. The latter feature has the practical advantage of interchangeability with present bicycle parts, thereby avoding axal position by a lock nut 2|, also threaded on to the section 19.

. Right and left cups or outer race rings 22` and 23 are set into the respective ends of the head I, being positioned in their inward axial movement 'by Shoulders which abut the ends of the head II.

One annular set of balls is interposed between the right cone I 6 and the right cup 22, and a similar annular set of balls 24 is interposed between the left cone 20 and the-left cup 23.`

The cones IB and 20 do not have conical ball engagingrsurfaces. Instead, the cone races are of the concave two-point contact type. Thus, re-

ferring for clarity to the enlax'ged detail section in Fig. 2, the annular ball race 20' of the cone 20 is so contoured in relation to the spherical surface'of a ball 24, that the ball makes contact With the ball race 20' at two points a and b. Contact at the point a takes most of the inward or radial thrust, and contact at the point b takes the axial thrust to the right and some of the radial thrust. The corresponding contact point on the ball race IE' of the right cone IG, as will be understood, takes the axial thrust to the left. The two bearing units thus hold the Crank against axial movement in either direction. i While still offering what is essentially aI twopoint contact, the contour of the ball race of the The retainer 25 is preferably formed from sheet stock and is in the form of ani annulus with a generally channel shaped radial crosssection. The channel cross-section comprises a web 25, an inner fiange 21, and an outer flange 23. A setJ of holes 29 of somewhat lesser diam- Veter than the balls is provided through the Web 26.

Prior to assernbly of the balls into the retainer, the flanges 21 and 28 of the characteristic channel cross-section are sp'read farther apart than shown in the drawing. The balls are set into ;the channels, one ball resting in each hole 29.

cone may, in practice, follow a radius as great as that of each ball.

an inter-'parallel band ofv a' spherical surfaceJ The center o-f the spherical surface is. on the axis of the shaftl portion.. As shown in .Fig..2, this spherical surface isdetermined` by `drawi-ng a i radiusr extending diametrically through one of the balls to bisect radiiv r'a and-rb from the center'of the ball 'to..the`contact points and b, and extendedzto the axis w; The point c where thel radius intersects the axis is theicenter of'the spherical'surface; and the length .oftheradius is the distance from the center c` to the far side of thebalL. i 1 T i .I[f-,V because ofy inaccuracies'; in Cutting the threads Vin the threaded; Sections of the shaft portion of the'crank,-or in the Vbores of the cones, or for other reasons, the ball engaging races of the cones do 4not hold the set of balls accurately in, afplane ata normal; to the axis, but V.instead permitlthesetof z'balls to rotate somewhat after ing" of the cones relative to the axis without im `pairingthev operation of the bearing or hastening its :area-ring. It 'does notinterfere with. the usual: axiaiadjnstme'nt vof the. bearing. .The improvementfrequi'res a' structural change only: in the cups, 'the other parts.l remaining .as before. This means that; the improvement canrbe incorporatedl existing bicycles merely 'byx'substituting'new cups.`` lfltz alsoimeans that. the; other i parts may7 cqntinue to beof existing design, instead; of? re-z quiring aV number of new parts in' lorder'toput' the ;the irmoro'vement into. commercial practice. :In l IVhai/Te showna modification in. which thetwo-pointtcontaot type of;` ballface is in- 'corporatedpin thecup? andmthe, inter-parallel spherical band iconstitutes .the .ball face of the; cone race. In that case, the vface isA convex rathery than concav. This reyerseiarrangement of 4 Eigs 4 is2 not; tlie'pfeferred form, 'howeven VAnother:phase 'ofxmyz inven'tion concernsfa rtainerring for these bearings. "i'rnezeontourer the ballengaging. faces'makes it almost neces- SaryV far? Com/eniem Commercial: assembly,V to: employ-aretai r ring Usual ,retainer'ringa howl everwi-ll: notz-fit or function in these bearings. Accordinglyt Ihaye; devised: a newV design of reta ine r25.` `j 1 Then the free edges of the fianges 21 and 28 are pressed toward each other until they contact the balls, w-'hich then prevents the balls from falling out of the retainer or from coming out of the holes 29. Thus, on the outer side of the retainer the balls protrude through the holes 29 and on the inner side of the retainer they protrude through the slot or open side of the channel between the edgesl of the flanges 21' and '2.8.

Unlike retainers frequently used in thrus-t bearings, the Web of my retainer is. not 'generally cylindrical, but instead is frusto-coinical. The

angle of the cone face vof the web complementsdicular to the axis of a line passing'from the aXs point C through the center of a balL state it in stillanother way, inl radial' cross section, the retainer is a channel, and the center line of the channel falls along the oblque. line 2.

My conicall-y cenlievrd retainer, inVoth-er words, has its radial section designed aboutan oblque axis, instead of about a Vertical a'xi's as the instance of a conizentional thrust bearing, re-H tainer, or aboutahorizpntal axis as inl a convene tional radial bearng'. Tlms,V those portiors` of the retainer which protrude beyond the pathsrof the-balls come in` the open space between the 'cup and cone where they do not interfere with other parts ofthe 'beari-ng;

, avingwthus described and illustrated ventiornwhat I claim'i: t i For journali-nga crank orthe like i-nits hanger,v

two coaxiall combination radiali andend thrustV ball'` bearines,` each: bearing comprising: a, cene member threadedupon and carried by the crank,

a cup memberpositicned: both radially outwardly. j

fromv and axiall-y inwardly of the. conez and: carriedby the hanger, and asingle annular setof: balls ridin'g between thecone' and' cup members;

: the ball race of o ne of the members being. annu-f larlyzcontoured. forsubstantially .two arcuately spaced points of, contact' with the balls', and; the ball race of the Other member being annularly`v contoured as an inter-parallel; band or zone of; aspherical surface whose; center is at. the interseotion lof the axis of the bearings and the extendedrdiameter of a ball, which diamet'er bisects radii of the ball pasing to its respective said contact points, the bearings. being axially spacedl apart a oonsiderabledistancel with the-fcentersfof saidl spherical surfaces of said) other members of i `the two bearings more widely spaced apartialong the axisA and axially outwardly of the planesi of the two. sets ofballs; g

FRANKW. scnwmn.

Or to i my in- 

